John J. Muccio, 89, a career diplomat and the first U.S. ambassador to South Korea. Muccio was ambassador in Seoul at the time of the North Korean invasion on June 25, 1950, and was in charge of evacuations and other critical matters during the height of the crisis. A native of Valle Agricola, Italy, Muccio grew up in Providence, R.I., and graduated from Brown University. He later received a master's degree in international relations from George Washington University. Muccio joined the U.S. Foreign Service in 1921. His overseas assignments included Hamburg, Hong Kong, Shanghai, La Paz, Panama City and Havana. He also served as ambassador to Iceland and Guatemala. In Washington on May 19 of congestive heart failure.